This invention relates generally to envelope generation in an electronic musical instrument and more particularly to a system for touch-responsive generation of an envelope waveshape in an electronic musical instrument of the keyboard variety.
In the co-pending application of William R. Hoskinson et al, Ser. No. 065,619, filed Aug. 19, 1979, now U.S. Pat. No. 4,299,153, a touch-responsive envelope control for a keyboard musical instrument is disclosed. The present invention represents an improvement upon this system. Accordingly, the present invention is particularly useful with a tone generator and keyer comprising an LSI circuit of the type disclosed in U.S. Pat. No. 4,203,337 to Schwartz et al. This LSI tone generating and keying circuit or chip will be hereinafter referred to as a B-2 chip, in conformity with its designation in the aforementioned patent.
The present invention, like the aforementioned Hoskinson et al co-pending application is directed to producing an envelope characteristic of a keyed tone approximating the response of a conventional percussion-type instrument such as a piano, in response to the velocity or intensity of the actuation of a key. In this regard, it has been found that the generally exponential charge and discharge characteristics of conventional capacitors provide a suitable approximation of both the attack and decay portions of such an envelope waveshape. However, in conjunction with digital LSI tone generating and keying chips of the type disclosed in the aforementioned Schwartz et al patent, it has heretofore been difficult to provide suitable charging and discharging signals corresponding to a relatively broad range of possible intensities of actuations of a key. Moreover, since as many as 16 separate tone generators and associated keyers may be provided in a typical keyboard instrument, it has heretofore proven difficult to assure the proper association of the charging signals generated in response to each key actuation with only the generator and keyer assigned to the production of the tone corresponding to that key.
In the foregoing Hoskinson et al application one such arrangement is disclosed. However, the present invention makes possible the same accuracy of control, while using fewer and less expensive circuit components. Accordingly, the present invention provides a relatively simpler and more economical system than heretofore available while permitting a broad range of peak intensities of an envelope generated for a particular tone, in accordance with the intensity of actuation of the associated key on the keyboard. Hence, a family of similar attack and decay envelope waveshapes may be provided, each having substantially similar attack time and decay rate, but a peak value to accordance with the intensity of key actuation and hence, a decay time in accordance with this peak value.